A new fabric becomes more breathable as you work up a sweat

Someday, the same shirt could be part of your summer and winter wardrobe, using fabric that alternates between breathable and insulating.

Unlike other heat-accommodating cloth, which has to be flipped inside out to switch from warm to cool (SN: 2/17/18, p. 5), the new dual-use fabric adapts to how much the wearer is sweating. This material may be useful for making sportswear or clothing for babies who can’t articulate when they’re too hot or too cold, says study coauthor YuHuang Wang, a chemist at the University of Maryland in College Park.

The fabric, described in the Feb. 8 Science, is knitted from yarn composed of many polymer fibers coated in tiny, carbon nanotubes. The closer these nanotubes are together, the better the fabric conducts the heat a person’s body sheds as infrared radiation.

Under cool, dry conditions, the fibers are loosely wound, and the fabric traps much of the heat radiating off the wearer’s body. But if the person starts to sweat, that humidity causes the polymer fibers in the yarn to constrict into tight bundles. This brings the carbon nanotubes on neighboring fibers closer together, making the material more breathable.

Wang and colleagues found that increasing the humidity inside a chamber containing a piece of the fabric could increase the amount of heat that passed through the material up to about 35 percent. The fabric’s dependence on water in the surrounding air means that even on a cool, muggy day when the user isn’t necessarily sweating, humidity in the surrounding air could make the fabric less insulating. In the future, Wang imagines making the yarn fibers with materials that respond directly to temperature changes, so the fabric can accommodate a person’s skin temperature as well as sweat levels.